Square kilometers to square miles (km² to mi²) converter

What is a square kilometers to square miles converter?

A square kilometers to square miles converter is an online tool that translates an area expressed in square kilometers into its equivalent in square miles, and back again. It connects the metric system, where land and surface areas are measured in square kilometers (km²), with the Imperial and US customary systems, where the square mile (mi²) is the standard large-area unit. This is helpful whenever you compare figures from sources that use different conventions, such as the size of a country, a national park, a watershed, or a metropolitan region.

How does the converter work?

Both units describe a two-dimensional area, so converting between them is a single multiplication by a fixed factor. One square kilometer equals about 0.386102 square miles, and one square mile equals about 2.589988 square kilometers. The converter applies the appropriate factor depending on which field you edit: type a value into the square kilometers field and it returns square miles instantly, or type into the square miles field to get square kilometers. Either side can also be switched to related units, such as square meters, so the same tool handles several area conversions at once.

Formula for conversion

The relationship between the two units rests on the definition of a mile, where 1 mile = 1.609344 kilometers. Squaring both sides gives the area factor.

To convert square kilometers to square miles: $\text{mi}^2 = \text{km}^2 \times 0.386102$

To convert square miles to square kilometers: $\text{km}^2 = \text{mi}^2 \times 2.589988$

If you also need square meters, remember that one square kilometer contains exactly one million square meters: $\text{m}^2 = \text{km}^2 \times 1{,}000{,}000$

Conversion table

The table below lists common square kilometer values and their square mile equivalents, with the reverse direction shown for convenience.

Examples

Example 1: One square kilometer to square miles

Convert 1 km² to square miles using the factor 0.386102:

$1 \text{ km}^2 \times 0.386102 = 0.386102 \text{ mi}^2$

Example 2: One square mile to square kilometers

Convert 1 mi² back to square kilometers using the factor 2.589988:

$1 \text{ mi}^2 \times 2.589988 = 2.589988 \text{ km}^2$

Example 3: A larger area

A protected area of 10 km² is being described to an audience that thinks in square miles. Multiply by the conversion factor:

$10 \text{ km}^2 \times 0.386102 = 3.861022 \text{ mi}^2$

Example 4: Square kilometers to square meters

To express the same square kilometer in square meters, multiply by one million:

$1 \text{ km}^2 \times 1{,}000{,}000 = 1{,}000{,}000 \text{ m}^2$

Notes

• The factor 0.386102 (km² to mi²) is simply the inverse of 2.589988 (mi² to km²), so the two directions are perfectly consistent.
• The conversion derives from the exact definition 1 mile = 1.609344 km; the rounded factors above are accurate to six decimal places for everyday use.
• Square miles here refer to the international (statute) mile, which is identical in the US customary and Imperial systems for this purpose.
• Keep units consistent across a whole project or document to avoid mixing metric and Imperial area figures.

Frequently asked questions

How many square miles are in a square kilometer?

One square kilometer equals approximately 0.386102 square miles. To convert any area, multiply the number of square kilometers by 0.386102.

How many square kilometers are in a square mile?

One square mile equals approximately 2.589988 square kilometers. Multiply the number of square miles by 2.589988 to get square kilometers.

How do I convert 10 square kilometers to square miles?

Multiply 10 by 0.386102, which gives about 3.861022 square miles.

Why is the area factor not the same as the length factor?

Because area is two-dimensional. A mile is 1.609344 km long, but a square mile is that figure squared, about 2.589988 km², so you must square the linear factor when converting areas. If you only need to convert lengths, use our length converter.

Can this converter handle other area units?

Yes. Each side can switch to units such as square meters, so you can convert square kilometers to square meters or work with several area units in one place. For a broader set of units, try the area unit converter.

Is the difference between US and Imperial square miles significant?

No. Both systems use the international statute mile for these calculations, so a square mile is the same area in each, and a single conversion factor applies.